#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
    int a = 0;
    int b = 0;
    scanf("%d", &a);
    scanf("%d", &b);
    int c = b - a;
    c /= 100;
    int x = c % 100;
    x /= 10;//x*=10;x/=100;
    int s = c % 60;
    c = c / 60;
    int m = c % 60;
    int h = c / 60;
    if (x > 5)
    {
        s++;
    }
    printf("%02d:%02d:%02d", h, m, s);
    return 0;
}
